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Background: When the skin is exposed to solar irradiation, UVA photons interact with skin tissues and induce excessive reactive oxygen species, resulting in oxidative stress. We have shown in a previous study that in vivo chemiluminescence's measurement can be used to evaluate the overall level of UVA-induced oxidative stress in human skin. However, the origin of the observed chemiluminescence signals remains unclear. Methods: UVA-induced chemiluminescence measurements were conducted: (a) in vitro on collagen solutions and solid collagen sheet preparations, (b) ex vivo on human and mouse skin biopsies, and (c) in vivo on human skin of various constitutive pigmentation levels. Fluorescence was measured on collagen in vitro as well as on skin for the in vivo experiments. Results: We found in the in vitro experiments that UVA-induced chemiluminescence increases with the presence of collagen cross-links. When dermal sides were exposed to UVA irradiation, both mouse and human skin biopsies demonstrated significantly higher chemiluminescence levels than when epidermal sides were exposed to UVA. The amount of collagen cross-links decreases slightly following UVA exposure, as shown both by in vivo fluorescence and by UVA-induced chemiluminescence. Finally, there was less measurable UVA-induced chemiluminescence in dark skin compared with light pigmented skin in vivo. Conclusions: The dermis is very sensitive to UVA photons. Dermal cross-links are potential UVA sensitizers. The oxidative stress induced by UVA and measured by chemiluminescence may largely be attributed to the breakdown of dermal collagen cross-links.

Skin water barrier development begins in utero and is believed to be complete by week 34 of gestational age. The goal of this investigation was to assess the dynamic transport and distribution of water of the stratum corneum of infants and compare it to those of adults. The interaction of water with the stratum corneum was assessed by measuring capacitance, transepidermal water loss (TEWL), rates of absorption-desorption as well as Raman spectra as a function of depth (a total of 124 infants (3-12 months) and 104 adults (14-73 years)). The results show that capacitance, TEWL, and absorption-desorption rates had larger values consistently for infant stratum corneum throughout the first year of life and showed greater variation than those of adults. The Raman spectra analyzed for water and for the components of natural moisturizing factor (NMF) showed the distribution of water to be higher and have a steeper gradient in infants than in adults; the concentration of NMF was significantly lower in infants. The results suggest that although the stratum corneum of infants may appear intact shortly after birth (

The objective of this study was to assess the efficacy of the combination of retinol, lactose and glycolic acid applied topically on photodamaged skin. Forty female volunteers were enrolled in a double-blind, randomized placebo-controlled clinical study. A cream containing retinol, lactose and glycolic acid was applied on one side of the face and a placebo cream on the other side, twice daily for 12 weeks. Skin photoageing signs were assessed clinically, whereas skin microrelief and moisturization were measured instrumentally. Both the clinical assessment and the objective instrumental measurements revealed that the active-treated side was significantly improved at the end of the study compared with baseline and control-treated side. In conclusion, our results demonstrate that topical application of a combination of retinol, lactose and glycolic acid has significantly improved the appearance of photodamaged skin.

Background Topical application of oils and oil-based formulations is common practice in skin care for both adults and infants. Only limited knowledge however is available regarding skin penetration and occlusive potential of oils and common methods for measuring skin moisturization fall short when it comes to the moisturizing effect of oils. Objective In this study we used in vivo confocal Raman microspectroscopy to test the efficacy of paraffin oil (mineral oil) and two vegetable oils in terms of skin penetration and occlusion. Petrolatum was used as a positive control. Methods The products were applied topically on the forearms of nine volunteers and seven infants and Raman spectra were acquired before and at 30 and 90 min following application. Depth concentration profiles for lipid and water were calculated from the Raman spectra. Skin occlusion was assessed from the amount of stratum corneum (SC) swelling measured from the water concentration profiles. Results The paraffin oil and the vegetable oils penetrate the top layers of the SC with similar concentration profiles, a result that was confirmed both for adult and infant skin. The three oils tested demonstrated modest SC swelling (10-20%) compared to moderate swelling (40-60%) for petrolatum. Conclusion These data indicate that there is no statistical difference between the paraffin oil and vegetable oils in terms of skin penetration and skin occlusion. The results for petrolatum show that in vivo confocal Raman microspectroscopy is sensitive and specific enough to measure both lipid uptake and skin occlusion events following topical application.

Tissue inflammation is often accompanied by local interstitial fluid accumulation expressed as edema. Edema can be the manifestation of infection, lymphatic blockage, wound healing, or even cancer, and is typically graded visually. Here we demonstrate that the edema reaction can be objectively quantitated in vivo by the use of spectral imaging. To this end we applied the method on a histamine-induced cutaneous edema model. Apparent concentrations of oxy-hemoglobin, deoxy-hemoglobin, and water were calculated for each pixel of a spectral image stack. These values were used to construct concentration maps for each of these molecules as well as an intensity map of an optical tissue-scattering parameter. The oxy-hemoglobin and the tissue water maps are two-dimensional quantitative representations of the skin areas involved in erythema and edema, respectively. These maps demonstrated characteristics of the wheal-and-flare reaction and their gray-level intensities were dependent on the applied histamine dose. We conclude that spectral imaging can be a valuable noninvasive tool in the study of edema pathology and can be used to monitor the edema reaction in vivo or follow the efficacy of treatments in a clinical setting.

Mineral oil in skin care is used as an emollient enhancing moisture retention in the skin. Toxicological studies in animals and tolerance studies in humans demonstrate the safety profile of pharmaceutical grade mineral oil.

Summary Background Throughout life facial skin is exposed to a variety of adverse environmental conditions and is constantly required to repair itself. The rate of epidermal cell proliferation is indicative of the skin's repair rate and can be monitored noninvasively in vivo using skin intrinsic fluorescence markers. Objectives The goal of the present study was to assess the effects of ageing, geographical region, ethnic origin and season on the ability of facial skin to repair itself in the presence of chronic environmental insults using in vivo fluorescence spectroscopy. Methods Skin fluorescence emission was measured on the cheeks of 522 individuals in winter and repeated in summer in five different geographical locations in the Asia-Pacific region. Fluorescence emission was also measured from 80 caucasians of fair complexion in the United States (New Jersey area) on the face and on a relatively protected area (upper inner arm). The age range of the participants was 14–75 years. Results We found that epidermal proliferation rates decrease monotonically with age, while the fluorescence of collagen and elastin cross-links increases with age indicating accumulation of advanced glycation end-products. These trends were independent of geographical region, ethnic origin and season of measurement. Epidermal proliferation rates of facial skin were higher than those of unexposed sites; they may be 10 times higher in younger (second decade) than in older (seventh decade) individuals, and they decrease with age at rates 10 times faster compared with those of unexposed sites. Conclusions This is the first time that epidermal proliferation and its dependence on ageing have been measured noninvasively on the human face. The higher tryptophan fluorescence values on the face vs. the protected site are indicative of accelerated rates of epidermal proliferation in the presence of chronic environmental insults. The repair potential of facial skin, i.e. its ability to maintain high proliferation rates, is maximal in younger populations and gradually decreases with age.

Summary Autofluorescent lipofuscin and advanced glycation end-products (age pigments) accumulate with age across phyla, yet little is understood about their formation under physiological conditions and their specific contributions to the aging process. We used in vivo spectrofluorimetry to quantitate autofluorescence in wild-type Caenorhabditis elegans and longevity mutants disrupted for distinct aspects of the aging process. In wild-type animals, age pigments increase into adulthood, accumulating slowly during the reproductive phase and more rapidly during the post-reproductive period. As in humans, insulin signaling influences age pigment accumulation – mutations that lower efficacy of insulin signaling and extend lifespan [daf-2(e1370) insulin receptor and age-1(hx546) PI3-kinase] dramatically lower age pigment accumulation; conversely, elimination of the insulin-inhibited DAF-16/FOXO transcription factor causes a huge increase in age pigment accumulation, supporting that the short-lived daf-16 null mutant is truly progeric. By contrast, mutations that increase mitochondrial reactive oxygen species production do not affect age pigment accumulation, challenging assumptions about the role of oxidative stress in generating these species in vivo. Dietary restriction reduces age pigment levels significantly and is associated with a unique spectral shift that might serve as a rapidly scored reporter of the dietary restricted state. Unexpectedly, genetically identical siblings that age poorly (as judged by decrepit locomotory capacity) have dramatically higher levels of age pigments than their same-aged siblings that appear to have aged more gracefully and move youthfully. Thus, high age pigment levels indicate a physiologically aged state rather than simply marking chronological time, and age pigments are valid reporters of nematode healthspan.

Objective in situ measurements of skin pigmentation are needed for accurate documentation of pigmentation disorders, in studies of constitutive and induced skin pigmentation, for testing of the efficacy of pro-pigmentation or de-pigmentation agents, etc. Non-invasive instrumental measurements of skin pigmentation have been used for many decades. All are based on the ability of melanin to attenuate light. However, hemoglobin in dermal capillaries also attenuates light and needs to be accounted for when pigmentation is assessed. The methods under consideration include: (a) single point measurements, in which light reflected from a defined skin area is collected and a pigment index is calculated representing the average pigmentation over the examined area, and (b) imaging methods that attempt to generate a concentration distribution map of melanin pigment for the skin area being imaged. In this article, we describe the potentials and the limitations of the different approaches to both single point and imaging methods.

Oxidative stress is defined as an imbalance between pro-oxidants and antioxidants in favor of pro-oxidants. Photon emission (also called chemiluminescence) has been widely used to study oxidative stress in biological systems in vitro. In vivo chemiluminescence has been proposed as a non-invasive method to assess oxidative stress in the skin. UVA (320-400 nm part of the ultraviolet radiation) exposure is generally accepted as a source of oxidative stress in the skin. In this study, UVA-induced oxidative stress was studied by using an in vivo chemiluminescence detection method. First, the dose response and the fluence rate response of the UVA-induced oxidative stress in human skin were investigated by examining the decay kinetics of the chemiluminescence signal following UVA exposure. A kinetic model was proposed to help differentiate these two responses. We found that the initial burst of the chemiluminescence signal depended on the UVA fluence rate, whereas the decay of the signal following exposure can be related to the UVA dose involved. Second, a significant reduction of UVA-induced chemiluminescence signal was observed after tape-stripping, indicating that stratum corneum is a major source of UVA-induced oxidative stress in the skin. Furthermore, the oxygen dependence of UVA-induced chemiluminescence signal was also confirmed by application of a pressure cuff, implying that some of the oxidative stress occurs in the deeper layers of the skin. Finally, topical application of vitamin C before exposure significantly reduced the UVA-induced chemiluminescence signal. We thus conclude that chemiluminescence is an effective method to assess the oxidative stress induced by UVA in human skin in vivo.

The purpose of this investigation was to study the ultraviolet A-induced effects on melanin pigmentation both in an in vitro model system and in vivo. Ultraviolet-Vis absorbance spectra of L-3,4-dihydroxyphenylalanine-melanin solutions at different concentrations were measured before and after ultraviolet A exposure (10–120 J per cm2). The difference spectra reveal that following ultraviolet A exposure the absorbance increases exponentially from 800 nm to 450 nm accompanied by a prominent decrease of absorbance in the ultraviolet A range. This change of spectral features depends on both ultraviolet A doses and melanin concentrations. The photo-bleaching effect observed in the ultraviolet A range also depends on oxygen. Human subjects were irradiated with ultraviolet A (40–80 J per cm2) on their back and diffuse reflectance spectra were collected at both irradiated and untreated sites. The absorption spectra of ultraviolet A-induced pigment were calculated as the difference of the two. The ultraviolet A-induced pigment in vivo has similar spectral characteristics and dose dependency as the in vitro system. Photo-oxidation of pheomelanin solutions presents distinctively different spectral and dose–response characteristics from eumelanin. After ultraviolet A irradiation pheomelanin absorbance decreases both in the visible and the ultraviolet A range. We conclude that irradiation with ultraviolet A induces significant photochemical alterations in the skin witnessed by increased photoprotection in the visible spectral range and reduced protection in the ultraviolet A range. We suggest that soluble melanin plays an important part in ultraviolet A-induced pigment in skin and two distinct absorption mechanisms of melanin may be involved in ultraviolet A photo-oxidation. We also propose that eumelanin and pheomelanin could be differentiated according to their spectral responses to ultraviolet A irradiation.

A number of noninvasive approaches have been developed over the years to provide objective evaluation of the skin both in health and in disease. The advent of computers, as well as of lasers and photonics, has made it possible to develop additional techniques that were impossible a few years ago. These approaches provide the dermatologist with sensitive tools to measure the skin's condition in terms of physiologic parameters (e.g., color, erythema and pigmentation, induration, sebaceous and stratum corneum lipids, barrier function, etc.). Yet, a typical dermatologic diagnosis relies primarily on the trained eyes of the physician and to a lesser extent on information from other senses, such as touch and smell. The trained senses of the dermatologist backed by his/her brain form a powerful set of tools for evaluating the skin. The golden rule in diagnosis remains the histologic examination of a skin biopsy, a rather invasive method. These tools have served the profession well. The advent of ever faster and cheaper computers and of sensitive, inexpensive optical instrumentation of minimal dimensions provides the professional with the possibility of making objective measures of a number of skin parameters.

The fluorescence properties of skin both human and of an animal model are reviewed in this article. Fluorescence spectroscopy is a valuable tool for the investigation of the optical properties of the skin in the ultraviolet range of the spectrum because the absorption bands are confluent. Epidermal and dermal fluorescence signals are each produced in distinct spectral regions. Biological processes modulate the fluorescence signals in predictable ways. Such cases include aging, epidermal proliferation, and photoaging as well as diseases such as psoriasis, acne and non-melanoma skin cancer. Fluorescence excitation spectroscopy has proved a valuable approach in the study of the structure and function of human skin. (C) 2002 Elsevier Science B.V. All rights reserved. Vibrational Spectroscopy

Topical application of active compounds on skin is common to both pharmaceutical and cosmetic industries. Quantification of the concentration of a compound deposited on the skin is important in determining the optimum formulation to deliver the pharmaceutical or cosmetic benefit. The most commonly used techniques to date are either invasive or not easily reproducible. In this study, we have developed a noninvasive alternative to these techniques based on spectrofluorimetry. A mathematical model based on diffusion approximation theory is utilized to correct fluorescence measurements for the attenuation caused by endogenous skin chromophore absorption. The limitation is that the compound of interest has to be either fluorescent itself or fluorescently labeled. We used the method to detect topically applied salicylic acid. Based on the mathematical model a calibration curve was constructed that is independent of endogenous chromophore concentration. We utilized the method to localize salicylic acid in epidermis and to follow its dynamics over a period of 3 d.

The stratum corneum (SC) provides a permeability barrier that limits the inflow and outflow of water. The permeability barrier is continuously and dynamically formed, maintained, and degraded along the depth, from the bottom to the top, of the SC. Naturally, its functioning and structure also change dynamically in a depth-dependent manner. While transepidermal water loss is typically used to assess the function of the SC barrier, it fails to provide any information about the dynamic mechanisms that are responsible for the depth-dependent characteristics of the permeability barrier. This paper aims to quantitatively characterize the depth-dependency of the permeability barrier using in vivo non-invasive measurement data for understanding the underlying mechanisms for barrier formation, maintenance, and degradation. As a framework to combine existing experimental data, we propose a mathematical model of the SC, consisting of multiple compartments, to explicitly address and investigate the depth-dependency of the SC permeability barrier. Using this mathematical model, we derive a measure of the water permeability barrier, i.e. resistance to water diffusion in the SC, from the measurement data on transepidermal water loss and water concentration profiles measured non-invasively by Raman spectroscopy. The derived resistance profiles effectively characterize the depth-dependency of the permeability barrier, with three distinct regions corresponding to formation, maintenance, and degradation of the barrier. Quantitative characterization of the obtained resistance profiles allows us to compare and evaluate the permeability barrier of skin with different morphology and physiology (infants vs adults, different skin sites, before and after application of oils) and elucidates differences in underlying mechanisms of processing barriers. The resistance profiles were further used to predict the spatial-temporal effects of skin treatments by in silico experiments, in terms of spatial-temporal dynamics of percutaneous water penetration.

Background/purpose The Stratum Corneum (SC) barrier function mainly depends on the SC structure at the tissue level, its composition, and the organization of intercellular lipidic cement at the molecular level. The goal of this study was to assess the age-dependent changes of the SC barrier function and the associated physiological parameters. Methods This study was conducted on 40 French women divided into four groups of age. Measurements were done on three sites: cheek, protected, and exposed arm sites. SC composition (water, lipid/protein ratio, cholesterol, and ceramides) was measured using Raman confocal microspectroscopy, skin surface hydration using skin conductance, and barrier function through transepidermal water loss (TEWL) measurements. Results Transepidermal water loss decreases slightly with age, which is partially explained by the age-dependent increase in SC thickness. This decrease is faster for the face compared to both arm sites. The lipid to protein ratio and lipid compactness decrease significantly with age only for the arm sites. Water concentration profiles only decrease very close to the skin surface. At all ages tested, the SC on the cheek showed significantly higher TEWL, water and lipid content and less thickness compared to the arm sites. Comparison of the exposed to unexposed arm site showed difference only for the lipid compactness at the older group studied. Conclusion Skin aging, body site and environmental exposure can affect the SC barrier function, its structure, and its lipid content. The thickening of the SC with age compensates for the decrease of the quantity and ordering of the lipidic cement.

Acne is a pleomorphic skin disease. The evolution of an acne lesion involves several stages (a) preclinical manifestations (noninflammatory lesions), (b) emergence of inflammatory lesions, (c) clearance, and (d) leftover marks such as post-inflammatory hyperpigmentation (PIH) and scars (affected dermal structures).

Recombinant human transforming growth factor beta1 (TGF-beta1) was incorporated into biodegradable microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) at 6 ng/1 mg microparticles. Fluorescein isothiocynate labeled bovine serum albumin (FITC-BSA) was coencapsulated as a porogen at 4 microg/1 mg of microparticles. The effects of PEG content (0, 1, or 5 wt %) and buffer pH (3, 5, or 7.4) on the protein release kinetics and the degradation of PLGA were determined in vitro for up to 28 days. The entrapment yield of TGF-beta1 was 83.4 +/- 13.1 and 54.2 +/- 12.1% for PEG contents of 0 and 5%, respectively. The FITC-BSA and TGF-beta1 were both released in a multiphasic fashion including an initial burst effect. Increasing the PEG content resulted in the decreased cumulative mass of released proteins. By day 28, 3.8 +/- 0. 1 and 2.8 +/- 0.3 microg (based on 1 mg microparticles) of loaded FITC-BSA and 3.4 +/- 0.2 and 2.2 +/- 0.3 ng of loaded TGF-beta1 were released into pH 7.4 phosphate buffered saline (PBS) from microparticles with 0 and 5% PEG, respectively. Aggregation of FITC-BSA occurred at lower buffer pH, which led to decreased release rates of both proteins. For microparticles with 5% PEG, 2.3 +/- 0.1 microg of FITC-BSA and 2.0 +/- 0.2 ng of TGF-beta1 were released in pH 7.4 buffer after 28 days, while only 1.7 +/- 0.3 microg and 1.3 +/- 0.4 ng of the corresponding proteins were released in pH 3 buffer. The degradation of PLGA was also enhanced at 5% PEG content, which was significantly accelerated at acidic pH conditions. The calculated half-lives of PLGA were 20.3 +/- 0.9 and 15.9 +/- 1.2 days for PEG contents of 0 and 5%, respectively, in pH 7.4 PBS and 14.8 +/- 0.4 and 5.5 +/- 0.1 days for 5% PEG in pH 7.4 and 3 buffers, respectively. These results suggest that PLGA/PEG blend microparticles are useful as delivery vehicles for controlled release of growth factors.

Recombinant human transforming growth factor β1 (TGF-β1) was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) to create a delivery vehicle for the growth factor. The entrapment efficiency of TGF-β1 in the microparticles containing 5% PEG was 40.3 ± 1.2% for a TGF-β1 loading density of 6.0 ng/1 mg of microparticles. For the same loading, 17.9 ± 0.6 and 32.1 ± 2.5% of the loaded TGF-β1 was released after 1 and 8 days, respectively, followed by a plateau for the remaining 3 weeks. Rat marrow stromal cells showed a dose response to TGF-β1 released from the microparticles similar to that of added TGF-β1, indicating the activity of TGF-β1 was retained during microparticle fabrication and after TGF-β1 release. An optimal TGF-β1 dosage of 1.0 ng/mL was determined through a 3-day dose response study for maximal alkaline phosphatase (ALP) activity. The TGF-β1 released from the microparticles loaded with 6.0 ng TGF-β1/1 mg of microparticles for the optimal dosage of TGF-β1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells cultured on poly(propylene fumarate) substrates. The cells showed significantly increased total cell number, ALP activity, and osteocalcin production with values reaching 138,700 ± 3300 cells/cm2, 22.8 ± 1.5 × 10−7 μmol/min/cell, and 15.9 ± 1.5 × 10−6 ng/cell, respectively, after 21 days as compared to cells cultured under control conditions without TGF-β1. These results suggest that controlled release of TGF-β1 from the PLGA/PEG blend microparticles may find applications in modulating cellular response during bone healing at a skeletal defect site. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 50, 452–462, 2000.

For the last 3 decades evidence has been accumulating that some types of mammalian cells respond to their mechanically active environment by altering their morphology, growth rate, and metabolism. The study of such responses is very important in understanding, physiological and pathological conditions ranging from bone formation to atherosclerosis. Obtaining this knowledge has been the goal for an active research area in bioengineering termed cell mechanotransduction. The advancement of optical methodologies used in cell biology research has given the tools to elucidate cellular mechanisms that would otherwise be impossible to visualize. Combined with molecular biology techniques, they give engineers invaluable tools in understanding the chemical pathways involved in mechanotransduction. Herein we briefly review the current knowledge on mechanical signal transduction in mammalian cells, focusing on the application of novel optical techniques in the ongoing research.

The smooth muscle cell (SMC) layers of human arteries may be exposed to blood flow after endothelium denudation, for example, following balloon angioplasty treatment. These SMCs are also constantly subjected to pressure driven transmural fluid flow. Flow-induced shear stress can alter SMC growth and metabolism. Signal transduction mechanisms involved in these flow effects on SMCs are still poorly understood. In this work, the hypothesis that shear stress alters the intracellular pH (pHi) of SMC is examined. When exposed to venous and arterial levels of shear stress, human aortic smooth muscle cells (hASMC) undergo alkalinization. The alkalinization plateau persisted even after 20 min of cell exposure to flow. Addition of amiloride (10 micromoles) or its 5-(N-ethyl-N-isopropyl) analog (EIPA, 10 micromoles), both Na+/H+ exchanger inhibitors, attenuated intracellular alkalinization, suggesting the involvement of the Na+/H+ exchanger in this response. The same concentrations of these inhibitors did not show an effect on pHi of hASMCs in static culture. 4-Acetamido-4'-isothio-cyanatostilbene-2,2'-disulfonic acid (SITS, 1 mM), a Cl-/HCO3- exchange inhibitor, affected the pHi of hASMCs both in static and flow conditions. Our results suggest that flow may perturb the Na+/H+ exchanger leading to an alkalinization of hASMCs, a different response from the flow-induced acidification seen with endothelial cells at the same levels of shear stress. Understanding the flow-induced signal transduction pathways in the vascular cells is of great importance in the tissue engineering of vascular grafts. In the case of SMCs, the involvement of pHi changes in nitric oxide production and proliferation regulation highlights further the significance of such studies.

The largest organ of the human body is the skin with its ~2 m2 surface area that envelopes the whole organism defining its physical border and which most importantly provides a barrier against internal organ dehydration and external penetration of noxious substances. The critical importance of the skin barrier is appreciated when it is lost such as in skin burns or compromised such as in atopic dermatitis, affecting the overall wellbeing of the individual. Moreover, it has been shown that the skin barrier function undergoes a maturation process during the first years of life. It is therefore of interest to identify skin care routines such as washing and bathing that would not be damaging to the skin barrier and if possible enhancing its protection. Furthermore, barrier enhancement aids in the prevention and treatment of certain conditions such as atopic dermatitis. Recent scientific discoveries in skin biology and formulation science have advanced the understanding of the regulatory mechanisms that control skin barrier homeostasis as well as our knowledge of skin-product interactions. Application of this knowledge has led to the design of appropriate skin care products and the design of tests that can demonstrate barrier-related benefits. This special issue of the Dermatology Research and Practice addresses these issues. The paper by L. Telofski et al. titled “The infant skin barrier: can we preserve, protect, and enhance the barrier?” provides an introduction to the recent findings on skin barrier maturation after birth that lasts for the first few years of life. The authors present on healthy skin barrier development as well as problems that can arise during infancy related to abnormal skin conditions and barrier integrity. They then discuss appropriate cleansing routines that should respect the distinct nature of infant skin and the use of emollients to protect and enhance the infant skin barrier function. In the paper titled “Management of patients with atopic dermatitis: the role of emollient therapy” by M. Mack Correa and J. Nebus, the authors discuss in more detail the use of emollients as baseline support therapy to the use of corticosteroids or calcineurin inhibitors. Prevention strategies are also presented and include appropriate skin care routines, avoiding allergic triggers, and regular use of emollients to improve the skin barrier function. Y. Valdman-Grinshpoun et al. present the dermatologist's point of view in treating and managing atopic dermatitis in their contribution titled “Barrier-restoring therapies in atopic dermatitis: current approaches and future perspectives.” This paper makes the link between skin barrier dysfunction and atopic dermatitis. It goes on to discuss the importance of skin barrier therapy approaches for its management including the use of corticosteroids and immunomodulators, as well as the potential requirement of short-term topical or systemic use of antibiotics in cases of infected lesions. Another barrier-related disease, contact dermatitis, is reviewed in the paper by Y. Yoshihisa and T. Shimizu titled “Metal allergy and systemic contact dermatitis: an overview.” Known metals common in our environment, such as nickel, cobalt, zinc, and chromium can result in allergic contact dermatitis. The authors present in vivo and in vitro diagnostic tests of metal sensitivity. Other aspects of skin barrier protection are covered by the following two papers: “Cleansing formulations that respect skin barrier integrity” by R. Walters et al. and “Methods to assess the protective efficacy of emollients against climatic and chemical aggressors” by R. Roure et al. The former presents information about innovations in mild surfactant technologies used in cleansing products. As cleansing is an everyday activity that brings these products in contact with the skin, it is important to understand what makes a surfactant potentially aggressive to the lipids of the stratum corneum that provide a large part of the skin's barrier function. The use of hydrophobically modified polymers as surfactants in skin cleansing products is being introduced to enhance the stability and size of micelles and therefore the mildness to the skin. The latter mentioned paper deals with in vivo skin protocols that are being used to assess the protective action of emollients on the skin. Such models simulate skin exposure to cold wind or to an irritant such as sodium lauryl sulfate. Data are then presented to demonstrate how these investigative methods can be used to show how exposures can impact skin barrier and skin protection. Georgios N. Stamatas Alex Zvulunov Paul Horowitz Gary L. Grove

Throughout infancy, skin differs from that of an adult in structure, function, and composition and has water-handling properties that are markedly distinct. Although competent to prevent dehydration, immature skin barrier function leaves infants especially vulnerable to the environment with potential for development of skin irritations elicited, for example, by contact with allergens or exposure to harsh climatic conditions. To this is added a relatively high risk for the development of the inflammatory disease atopic dermatitis. Specially formulated moisturizers are thus needed that respect the specific properties of infant skin and protect it by enhancing the barrier properties without interfering with the natural development.

Confocal Raman Microspectroscopy was used to compute the concentration profiles of topically applied caffeine through the skin. Parameters relating to the skin barrier function were calculated from the caffeine concentration profiles.

In recent years, there have been continuing efforts to understand the effects of baby skin care routines and products on the healthy development of baby skin. Such efforts aim ultimately to determine the best infant skin care practices. The pediatric and dermatologic communities have not reached consensus on what constitutes an appropriate cleansing practice. In the United States, guidelines for neonatal skin care have been developed, propagated, and implemented. The accumulated knowledge has promoted evidence-based clinical practices and, therefore, may help to improve clinical outcomes, although these guidelines primarily cover the care of preterm newborns and the treatment of those with other health problems. High-level, long-term clinical evidence of the effective and safe cleansing of healthy, full-term newborns and infants is scarce. This review presents a comprehensive analysis of the scientific literature on baby skin development, cleansing practices, and related products (for healthy newborns and babies) since 1970. The evidence drawn from the reviewed literature can be summarized as follows: Bathing immersed in water seems generally superior to washing alone. Bathing or washing with synthetic detergents (syndets) or mild liquid baby cleansers seems comparable with or even superior to water alone. Nevertheless, larger randomized clinical trials with age-defined cohorts of babies as well as more-defined parameters are required to identify optimal practices and products for skin cleansing of healthy infants. These parameters may include standardized skin function parameters such as transepidermal water loss, stratum corneum hydration, skin surface pH, and sebum production. Clinical skin scores such as the Neonatal Skin Condition Score may be employed as outcome measures.

Within days after birth, rapid surface colonization of infant skin coincides with significant functional changes. Gradual maturation of skin function, structure, and composition continues throughout the first years of life. Recent reports have revealed topographical and temporal variations in the adult skin microbiome. Here we address the question of how the human skin microbiome develops early in life. We show that the composition of cutaneous microbial communities evolves over the first year of life, showing increasing diversity with age. Although early colonization is dominated by Staphylococci, their significant decline contributes to increased population evenness by the end of the first year. Similar to what has been shown in adults, the composition of infant skin microflora appears to be site specific. In contrast to adults, we find that Firmicutes predominate on infant skin. Timely and proper establishment of healthy skin microbiome during this early period might have a pivotal role in denying access to potentially infectious microbes and could affect microbiome composition and stability extending into adulthood. Bacterial communities contribute to the establishment of cutaneous homeostasis and modulate inflammatory responses. Early microbial colonization is therefore expected to critically affect the development of the skin immune function.

The skin is increasingly recognized as a component of the innate immune response, in addition to its role as a physical barrier. Although the deleterious effects of solar ultraviolet radiation (UVR), including immunosuppression and cutaneous tumorigenesis, are widely acknowledged, most studies to date have concentrated on adult skin. Despite the more sensitive nature of infant and toddler skin, little is known about its responses to UVR exposure, whether acute or long-term. Accumulating evidence suggests not only that the skin's barrier protection remains immature throughout at least the first 2 years of life but also that accumulation of UVR-induced changes in the skin may begin as early as the first summer of life. Such evidence not only affirms the importance of sun protection during the infant and toddler years but underscores the need for more research to establish evidence-based standards of care in this area. In this article we review recent studies in which differences between the skin properties of infants and young children and those of adults were compared, and we discuss the implications of these differences for sun-protection practices.

The presence of irritants from feces and urine with the concurrent mechanical friction and occlusion creates an environment in the diapered area that renders the skin prone to diaper dermatitis. Besides being a source of discomfort to the infant, these skin irritations pose a risk of secondary infections. In this study, we used noninvasive in vivo techniques to define measurable parameters that correlate with diaper dermatitis pathophysiology. In 35 infants (16 with mild or moderate and 19 without diaper dermatitis) we compared skin of diapered areas afflicted with diaper dermatitis to lesion-free diapered sites and to skin outside the diapered area (thigh). Our findings show significantly elevated cutaneous erythema, pH, and hydration, with significantly compromised water barrier function in involved areas compared to nonlesional sites both within and outside the diapered area. Furthermore, skin pH in nonlesional diapered skin for the diaper dermatitis cohort was significantly higher compared to the nondiapered sites. These observations are consistent with the current understanding of pathological skin changes in diaper dermatitis. In this study, we demonstrate that noninvasive methods can document relevant parameters to diaper dermatitis in vivo.

Due to metabolic processes inside the body, most nutrients cannot be detected directly on skin, and only a few might be detected in either their original molecular form or as one of their metabolic products. Based on their Raman spectral fingerprint, lycopene and β-carotene can be detected noninvasively on skin. Their apparent concentration increases with a carotenoid-rich diet. Nutritional lipid uptake can be detected on the lips using infrared spectroscopy. Immediate and long-term effects of nutrition may be quantitatively evaluated using noninvasive optical methods.

Pharmaceutical and cosmetic industries are concerned with treating skin disease, as well as maintaining and promoting skin health. They are dealing with a unique tissue that defines our body in space. As such, skin provides not only the natural boundary with the environment inhibiting body dehydration as well as penetration of exogenous aggressors to the body, it is also ideally situated for optical measurements. A plurality of spectroscopic and imaging methods is being used to understand skin physiology and pathology and document the effects of topically applied products on the skin. The obvious advantage of such methods over traditional biopsy techniques is the ability to measure the cutaneous tissue in vivo and non-invasively. In this work, we will review such applications of various spectroscopy and imaging methods in skin research that is of interest the cosmetic and pharmaceutical industry. Examples will be given on the importance of optical techniques in acquiring new insights about acne pathogenesis and infant skin development.

The antiaging efficacy of retinol (ROL) has been explored mainly clinically in photoprotected skin sites and for high doses of ROL (0.4–1.6%). The objective of the study was to demonstrate the antiaging action of a low and tolerable dose of ROL (0.1%) ex vivo by measuring the expression of cellular retinoic-acid-binding protein II (CRABP2) and heparin-binding epidermal growth factor (HBEGF) by a histological evaluation of the epidermis and in vivo by assessing major aging signs and performing three-dimensional profilometry and digital imaging during a 9-month double-blind placebo-controlled study involving 48 volunteers. Finally, epidermal cell proliferation was evaluated using tryptophan fluorescence spectroscopy. Our results demonstrate that 0.1% ROL induced CRABP2 and HBEGF gene expression and increased keratinocyte proliferation and epidermal thickness. In human volunteers, topical application of a ROL-containing product improved all major aging signs assessed in our study (wrinkles under the eyes, fine lines and tone evenness). Moreover, tryptophan fluorescence increased in the active-agent-treated group and not in the placebo-treated group, indicating that cell proliferation was accelerated in vivo. These data demonstrate that a product containing a low dose (0.1%) of ROL promotes keratinocyte proliferation ex vivo and in vivo, induces epidermal thickening ex vivo and alleviates skin aging signs, without any significant adverse reaction.

Background and objective The facial appearance of a person does not always reflect the chronological age; some people look younger or older than they really are. Many studies have described the changes in skin properties (colour, wrinkles, sagging, micro relief, etc.) with age, but few of them have analysed their influence on the perceived age. The primary objective of this study was to assess the contribution of individual skin attributes of the face on the perceived age of Caucasian women. Secondary objectives were to assess the influence of age and gender of graders with regard to the age perception. Subjects and method A random sample of 173 subjects of 20 to 74 years of age was taken from a database of more than 5000 healthy Caucasian women. A trained grader performed visual assessment of facial skin attributes (using a visual analogue scale), and a front face photograph was taken from each subject. Photographs were shown to 48 graders (20 men and 28 women, aged 22–64 years) who were asked to estimate the age of the subjects. Graders were classified as young (less than 35 years), middle age (35–50 years) and seniors (older than 50 years). Partial Least Square regression models were built to predict the chronological and the perceived age from the measured facial individual attributes. The contribution of each attribute within the regression model enabled to measure the relevance of this attribute with regards to age prediction. Results The eye area and the skin colour uniformity were the main attributes related to perceived age. For age prediction, older graders’ estimations were more driven by lips border definition shape and eyes opening, whereas younger graders’ (older than 50 years) estimations were more driven by dark circles, nasolabial fold and brown spots. There were statistically significant differences in graders’ age perception between gender and among age ranges. Our findings suggest that female graders are more accurate than male, and younger graders (under 35 years) are more accurate than older (over 50 years) to predict Caucasian women age from facial photographs. Conclusions Different skin attributes influence the estimation of age. These attributes have a different weight in the evaluation of the perceived age, depending on the age and of the observer. The most important attributes to estimate age are eyes, lips and skin colour uniformity.

Summary Background Various physical, chemical and biological insults, including exposure to ultraviolet (UV) radiation, cause erythema and change in pigmentation in human skin. These reactions provide an important measure of the cutaneous response to the insult. Objectives To present a new implementation of a method for objective in vivo measurement of erythema and pigmentation. Methods The method is based on acquisition of reflectance spectra in the visible range using a commercially available spectrophotometer. The probe of this instrument incorporates an integrating sphere that captures the light remitted from the skin in a wide range of angles. We corrected the acquired reflectance spectra for the contribution of specular reflections by an amount given by the Fresnel equation and verified this correction experimentally. This correction is particularly important when measurements are performed on heavily pigmented skin. The corrected reflectance spectra are then transformed into absorbance spectra. To analyse these spectra, we developed an algorithm which can be used to calculate apparent concentrations of oxyhaemoglobin, deoxyhaemoglobin and melanin. This method was tested in clinical studies of skin reactions induced by exposure to UV radiation. These experiments involved three groups of subjects with progressively darker complexion (constitutive pigmentation). Each group consisted of 10 subjects. Erythema was measured 1 day after UV exposure, and pigmentation (melanin content) 1 week later. Results Distinct apparent absorbance spectra were obtained for dark, intermediate and fair skin. There was good agreement between reconstructed spectra and experimental data at relevant wavelengths. Difference absorption spectra were able to show the dose dependence of UV-induced responses, and erythema and pigmentation values obtained by the spectroscopic method showed good correlation with those derived by subjective visual grading. Conclusions The results demonstrate that the presented methodology provides an objective noninvasive way of measuring UV-induced reactions independently of the level of constitutive pigmentation.

Typical manifestations of cutaneous inflammation include erythema and edema. While erythema is the result of capillary dilation and local increase of oxygenated hemoglobin concentration, edema is characterized by an increase in extracellular fluid in the dermis, leading to local tissue swelling. Both of these inflammatory reactions are typically graded visually. We demonstrate the potential of spectral imaging as an objective noninvasive method for quantitative documentation of both erythema and edema. As examples of dermatological conditions that exhibit skin inflammation we applied this method on patients suffering from (1) allergic dermatitis (poison ivy rashes), (2) inflammatory acne, and (3) viral infection (herpes zoster). Spectral images are acquired in the visible and near-IR part of the spectrum. Based on a spectral decomposition algorithm, apparent concentrations maps are constructed for oxyhemoglobin, deoxyhemoglobin, melanin, optical scattering, and water. In each dermatological condition examined, the concentration maps of oxyhemoglobin and water represent quantitative visualizations of the intensity and extent of erythema and cutaneous edema, correspondingly. We demonstrate that spectral imaging can be used to quantitatively document parameters relevant to skin inflammation. Applications may include monitoring of disease progression as well as screening for efficacy of treatments.

A rotationally invariant algorithm was developed to evaluate the orientation direction and orientation coherence of features in a two-dimensional image. The algorithm was validated on test images and was applied on in vivo confocal microscopy images to extract information on collagen matrix orientation and on skin microrelief images for the calculation of the primary direction of microglyphics.

Skin inflammation is often accompanied by edema and erythema. While erythema is the result of capillary dilation and subsequent local increase of oxygenated hemoglobin (oxy-Hb) concentration, edema is characterized by an increase in extracellular fluid in the dermis leading to local tissue swelling. Edema and erythema are typically graded visually. In this work we tested the potential of spectral imaging as a non-invasive method for quantitative documentation of both the erythema and the edema reactions. As examples of dermatological conditions that exhibit skin inflammation we imaged patients suffering from acne, herpes zoster, and poison ivy rashes using a hyperspectral-imaging camera. Spectral images were acquired in the visible and near infrared part of the spectrum, where oxy-Hb and water demonstrate absorption bands. The values of apparent concentrations of oxy-Hb and water were calculated based on an algorithm that takes into account spectral contributions of deoxy-hemoglobin, melanin, and scattering. In each case examined concentration maps of oxy-Hb and water can be constructed that represent quantitative visualizations of the intensity and extent of erythema and edema correspondingly. In summary, we demonstrate that spectral imaging can be used in dermatology to quantitatively document parameters relating to skin inflammation. Applications may include monitoring of disease progression as well as efficacy of treatments.

The chromatic characteristics of skin color arise from the interactions of light (primarily absorption and scattering) with the epidermis and the dermis. The primary light absorbers in skin are hemoglobin and melanin. Most of scattering is attributed to collagen fibers and in pigmented skin to melanosomes. Traditionally skin redness is considered to arise due to locally elevated concentrations of hemoglobin, whereas skin pigmentation is attributed to melanin. In this study we attempt to understand better the contributions of these chromophores to the perceived skin color using spectral analysis of skin color reactions induced by ultraviolet (UV) irradiation or pressure. In the first experiment 12 individuals with skin phototypes III-IV were irradiated on the back using a solar simulator with doses ranging from 0.7 to 3 MED. The skin reactions were evaluated on days 1, 7, 14, and 21 after irradiation. Evaluations included diffuse reflectance spectroscopy (DRS) and clinical assessment of the erythema and the pigment reaction. Apparent concentrations of melanin, oxy-, and deoxy-hemoglobin were calculated from the absorption spectra. In the second experiment the levels of deoxy-hemoglobin of the volar forearm of ten volunteers were selectively altered by either application of a pressure cuff or by topical application of 3% H(2)O(2). Changes in skin color appearance were documented by photography, colorimetry, and DRS. In the UV exposure experiment all reactions were dose dependent. Oxy-hemoglobin values increased to a maximum on day 1, correlating well with the clinical evaluation of erythema, and then decreased exponentially to base line. Melanin showed a significant increase on day 7 and remained relatively constant for the next 3 weeks, correlating well with the clinical evaluation of pigmentation (tanning). Deoxy-hemoglobin increased slightly on day 1 and remained elevated for the next 2 weeks. Thus, deoxy-hemoglobin correlated moderately with the clinical erythema scoring on day 1 only, while it contributes significantly to what is clinically perceived as skin tanning on days 7 and 14. Application of pressure below the diastolic level increased deoxy-hemoglobin concentration as measured by DRS. This increase corresponded to a decrease of a "pigmentation" parameter (based on the L(*)a(*)b(*) scale) in a similar fashion that has been documented for increases in melanin concentration. Topical H(2)O(2) application reduced deoxy-hemoglobin levels as measured by DRS. This reduction coincided kinetically with a visible skin blanching. Application of pressure or H(2)O(2) did not significantly alter the levels of oxy-hemoglobin or melanin. In this report we present compelling evidence that deoxy-hemoglobin significantly contributes to the skin color appearance. Blood pooling, expressed as increased deoxy-hemoglobin, can contribute to what is visually perceived as pigmentation. Furthermore, we present that measurement of its contribution to the skin color appearance can only be accomplished with DRS.

In vivo non-invasive methods are presented for the objective quantification of histamine-induced cutaneous edema based on hyper-spectral imaging and 3D profilometry. The measured parameters include extracellular water accumulation, hemoglobin concentration, edema height, and edema volume.

Hyperspectral imaging of skin combines the spectral information of diffuse reflectance spectroscopy with the spatial information of 2D imaging. Skin chromophore maps can be reconstructed in which features such as pigmented lesions, diffuse and localized erythema, areas of increased blood stasis, etc. could be identified and the relative parameters quantified. Hyperspectral imaging is the only reliable method to produce a quantitative distribution map of chromophores contributing to the color appearance of the skin.

Methods An interdisciplinary team of hospital and community agencies reviewed literature, examined current practices, and identified strategies for changes to improve outcomes and decrease readmissions for hyperbilirubinemia. Evidencebased practice changes were led by nursing leadership, pediatricians, unit practice committee, and quality committee. Education for nurses, pediatricians, and social workers was essential. Interventions addressed improved risk assessment, breastfeeding support in hospital and after discharge, timely availability of home phototherapy equipment, and establishment of consistent home health follow-up. Collaboration and relationship building between the healthcare system and community agencies were key to our success.

Skin reactions to stimuli such as UV irradiation include vascular changes and stimulation of melanin production. Both reactions alter the color appearance of the skin. Skin color reactions were evaluated visually by a trained dermatologist and using a diffuse reflectance spectrometer in the visible range. Our results provide strong evidence that mixed vascular and pigment reactions cannot be visually separated. The involvement of each chromophore can only be identified spectroscopically.

We have strong evidence that mixed vascular and pigment reactions cannot be visually separated and that blood stasis can be confused with pigmentation. The involvement of each chromophore can only be identified spectroscopically.

Endothelial cells alter their morphology, growth rate, and metabolism in response to fluid shear stress. To study rapid flow-induced responses in the 3D endothelial cell morphology and calcium distribution, coupled fluorescence microscopy with optical sectioning, digital imaging, and numerical deconvolution techniques have been utilized. Results demonstrate that within the first minutes of flow application nuclear calcium is increasing. In the same time frame whole cell height and nuclear height are reduced by about 1 microm. Whole cell height changes may facilitate reduction of shear stress gradients on the luminal surface, whereas nuclear structural changes may be important for modulating endothelial growth rate and metabolism. To study the role of the cytoskeleton in these responses, endothelial cells have been treated with specific disrupters (acrylamide, cytochalasin D, and colchicine) of each of the cytoskeleton elements (intermediate filaments, microfilaments, and microtubules, respectively). None of these compounds had any effect on the shear-induced calcium response. Cytochalasin D and acrylamide did not affect the shear-induced nuclear morphology changes. Colchicine, however, completely abrogated the response, indicating that microtubules may be implicated in force transmission from the plasma membrane to the nucleus. A pedagogical model based on tensegrity theory principles is presented that is consistent with the results on the 3D endothelial morphology.